Locating enemy-gun positions



R. A. FESSENDEN. LOCATING ENEMY GUN POSITIONS.

APPLICATION FILED APR. I9, 1918.

Patented June 1, 1920.

Heu/ff 2 i INVENTOR.

v T all whom t may concern:

UNITED srA'rEs` .PATET oFFlcE.

REGINALD A. FESSllNllUiiN-y 0F BROOKLINE, MASSACHUSETTS, ASSIGNOR TO SUBMARINE SIGNAL COMPANY, OF PORTLAND, MAINE, A CORPORATION OF MAINE.

LOCATING ENEMY-GN POSITIONS.

Be it known that I, REGINALD A. FEs- SENDEN, of Brookline in the county of Norfolk and State of Massachusetts, a citizen of the United States, have invented new and useful Improvements in Locating Enemy-Gun Positions, of Which the following is the specification.

My invention relates to the location of enemy gun positions and has for its object increased efficiency in locating such pos1- tions.

In the drawings accompanying this speclication, Figures 1 and 2 show, partly diagrammatically, means for accomplishing these results, and Fig 3 shows a portion of one of the records which may be utilized for obtaining the yresults desired.

As is Well known in Warfare, the territory in the neighborhood of the fighting line is divided into squares of any suitable area; for example, in artillery Work, the squares may be twenty-five yards on the side.

Such a square, 11, in which an enemys gun 12 is located is shown in Fig. 1. 13, 14, '15 are microphones placed back of our own line, and any suitable distance-for ex-A ample, one-half mile or a mile-apartthe microphones being provided with megaphone funnels 13, 14'-, 15 so as to enable them better to receive the sound of the gun 12 when fired,iand also to enable them to shut off to a certain extent thesound of guns fired from the rear or from one side.

These microphones are connected to the receivers 16, 17, 18 by circuits containing batteries .40, 41, 42, as shown.

The receivers 16, 17, 18 are preferably Vlocated in a sound proof receivers -booth and the observer is provided with a chronograph, or other suitable time measuring apparatus.

The observer first listens in on telephones 16 and 17 and, in the case shown, Will hear the sound of the gun 12 when fired on the receiver 17 before he hears it on the receiver 16. l

Immediately on hearing the sound of the gun in the receiver 17 the observer depresse's thech'ronograph key and later, on hearing it in the receiver 16, presses the key a second time. From the measured difference in the indications on ythe chronograph he is able to tell the difference in the Specification of Letters Patent.

- Patented June 1, 1920.

191s. serial No. 229,634.

times taken by the sound of the gun to arrive at the microphones 13 and 14 and, knowing the velocity of sound in air, to determine how much farther away the gun is from 13 than from 14. Let the difference in distance so called be A. Takinga map the observer then describes a circle 43, having its center at thelocation of the microphone 13 and its radius equal to A.

ISimilarly', by listening in on the receivers 17 and 18, the observer determines the difference in the distance from the microphone 14 to the gun and from the microphone 15 to the gun, which distance We will call B. The observer then draws a similar circle 44 on the map with its center at the location of the microphone 15 and having its radius equal to B. The gun 12 Will obviously be at the center of the circle Whose circumference touches the circle 43, the circle 44, and the location of the microphone v14, Which is easily determined by ordinary geometric means.

If desired, the observer may listen in on the microphones 16 and 18, and in this way obtain a check on the location of the gun 12 determined by listening in on the receivers 16 and 17 and then on the receivers 17 and 18. t,

In place of using microphones responsive to Waves transmitted through the air, as shown above, the microphones may be so arranged as to be responsive to the shock produced by the discharge of the gun and transmitted through the ground.

Suitable means for doing this are shown in Fig. 2, Where 45 is the surface of the ground; 28 ,is a pail immersed in the ground, containing a suitable fiuid 30--for example, Water. The microphone 29 is immersed in the liquid, and 31 are the conductors leading from the microphone. This arrangement is very' sensitive to tremors or shocks transmitted through the ground.4

If desired, some of the microphones may be used for receiving -the sound of discharge transmitted through the air and some may be used yfor receiving the discharge shock transmitted through the ground, the distance being found from the different velocities With which sounds travel through air and through round.

In place o using a chronograph of the ordinary type a recording filament galvanometer of the type invented by the Writer shape of these curves is in general different microphone `method, and: only possible, so far as appllmicrophones ,14 and 15.

i and described by him at the American Association for the Advancement of Science in 1892 and commonly known as the Einthoven galvanometer may-be used. The Einthoven galvanometer is well known to those skilled in the art. Two forms of this instrument are illustrated and described in ap licants'U. S.'

Patents No. 979,145, issued filed Dec. 23, 1907, and No. 1,045,782, issued Nov. 26, 1912, filed J an. 29, 1910. In Fig. 2 of the latter patent is shown a type in which the record is made on a moving 4strip of photographic film.

In this case two iilaments are preferably used, being connected severally first to the microphones 13 and 14 and then to the record such as has been obtained from the two microphones 13 and 14. In this figure 24 is astrip of the photographic recordingv filament and 26 represents the record obtained from one filament and microphone from the discharge of the gun 12, and 26 the record identified; for example 27, 27 being different in shape from 26, 26 may be identified as the record of some other gun, andthe location of this other gun may also be similarly obtained. This is possible because by this i method, as distinguished from the microphone method or the chronograph method, the curves showing the variation of sound with time for-each individual gun are accurately reproduced, and since the for each individual gun, each gun may be identified, which is not possible with the or ordinary chronograph cant knows, by this method. The official reports on these various types of a plicants l apparatus are to the elect that t e microphone and chronograph are only useful where the number of guns firingv is very limited, but that the wire galvanometer, or

Fig. 3 shows aas applicant terms it, the pallo aph method 1s satisfactory even in cases o very heavy, almost continuous firing.

In place of using two filaments connected to two microphones, three 'filaments may be used in the galvanometer and these may be connected to the three microphones so that the records from the gun 12 may all beproduced on the same piece of photographic record strip, as described in a plicants memorandum to the British War 4 Hice and U. S. Ordnance Board, No. J1, September l12, 1914. f

This method may also be applied to locating similar bodies; for example, Zeppelins and aeroplanes, as stated in U. S. application 35,957, June 23, 1915, of which the present application is a continuation as to all matter common to both applications. By the term enemy gun position is y meant any position' from which projectiles oscillograph at a predetermined rate whereby the intensities and times of arrival of the sounds produced by a number of guns fired approximately simultaneously are recorded and the sound produced by the individual guns-may be identified.

2. Means for' determiningthe location of enemy gun positions comprising a plurality of electric sound-receiving mechanisms located at a distance from each other and from the enemy gun positionswhich are to be located, a string oscillograph provided with a plurality of strings, said strings being operatively connected to said electric receiving mechanisms and means for observing the movements of said .strings produced by said electric sound-receiving mechanisms on the arrival of the sounds of the discharges of saidenem uns.

- RE I ALD A. FESSENDEN. 

